The adducts AsX3.3L [where L = benzenamine (An), 2-nitrobenzenamine (o-NO2An), 3-nitrobenzenamine (m-NO2An), or 4-nitrobenzenamine (p-NO2An) and X = Cl, Br, or I] were synthesized and characterized by melting points, elemental analysis, thermal studies, and infrared spectroscopy. From calorimetric studies in solution, the mean standard enthalpies of the arsenic-nitrogen bond were determined.